1. Field of the Invention
This invention relates to an organic electroluminescent (EL) device, and more particularly, to a compound for use in a device of the type wherein an electric field is applied across a thin film of an organic compound to emit light.
2. Background Art
Organic electroluminescent (EL) devices include a thin film containing a luminescent organic compound interleaved between an electron injecting electrode and a hole injecting electrode. Electrons and holes are injected into the thin film where they are recombined to create excitons. Light is emitted by utilizing luminescence (phosphorescence or fluorescence) upon deactivation of excitons.
The organic EL devices are characterized by plane light emission at a high luminance of about 100 plus to about 10,000 plus cd/m2 with a voltage of about 10 volts and light emission in a spectrum from blue to red color by a simple choice of the type of fluorescent material.
Doping is one technique for producing light emission of any desired color from organic EL devices. It was reported in Jpn. J. Appl. Phys., 10, 527 (1971) to change emission color from blue to green by doping anthracene crystals with a minor level of tetracene. With respect to organic thin film EL devices having a multilayer structure, it was reported in JP-A 63-264692 to incorporate in a host material having a light emitting function a minor amount of a fluorescent dye capable of emitting light different from that of the host material in response to light emission from the host material as a dopant to form a light emitting layer, thereby changing the color of light emission from green to orange or red.
With respect to long wavelength light emission of yellow to red, known light emitting materials or dopant materials include laser dyes capable of red oscillation (EPO 281381), compounds capable of exciplex emission (JP-A 2-255788), coumarin compounds (JP-A 3-792), dicyanomethylene compounds (JP-A 3-162481), thioxanthene compounds (JP-A 3-177486), mixtures of a conjugated polymer and an electron transporting compound (JP-A 6-73374), squalirium compounds (JP-A 6-93257), oxadiazole compounds (JP-A 6-136359), oxynate derivatives (JP-A 6-145146), and pyrene compounds (JP-A 6-240246).
It is reported in J. Am. Chem. Soc., 118, 2374-2379, 1996, that benzofluoranthene derivatives have a very high fluorescent quantum yield. JP-A 10-330295 and JP-A 11-233261 disclose organic EL devices having a light emitting layer in which a variety of host materials are doped with dibenzo[f,f′]diindeno[1,2,3-cd:1′,2′,3′-lm]perylene derivatives derived from benzofluoranthene.
For the synthesis of perylene derivatives encompassing such benzofluoranthene derivatives, it is a common practice to conduct synthesis using starting reactants of the following formulae (A), (B) and (C) and catalysts.

However, these prior art synthesis procedures suffer from the problem of very low efficiency because the end products are obtained in yields of at most 20%. Although the prior art synthesis procedures are relatively easy to synthesize an end product having symmetry, they encounter a problem when it is desired to obtain an end product having no symmetry. That is, since it is difficult to directly synthesize the asymmetric end product, the asymmetric end product must be separated from a variety of reaction products, which indicates a very low preparation efficiency and restricts the degree of freedom of compound design.